Does a forum handle represent higher security by itself? No. But it also is less likely to exist and be used in multiple places across the internet. So it is less prone to hacker based proliferation of attack.
Wrong. Most gamers/forum users use the same forum name in every game they play. Really, while this change doesn't make it any less secure, it really doesn't make it more secure either.
Like I said above, if they really wanted to make it more secure they should be telling us to create a new unique Account Name. CoH did something similar once upon a time and that's what they did.